Solar energy using photovoltaics requires active semiconducting materials to convert light into electricity. Currently, solar cells based on silicon are the dominating technology due to their high-power conversion efficiency. Recently, solar cells based on organic materials showed interesting features, especially on the potential of low cost in materials and processing.
Organic photovoltaic cells have many potential advantages when compared to traditional silicon-based devices. Organic photovoltaic cells are light weight, economical in the materials used, and can be deposited on low cost substrates, such as flexible plastic foils. However, organic photovoltaic devices typically have relatively low power conversion efficiency (the ratio of incident photons to energy generated). This is, in part, thought to be due to the morphology of the active layer. The charge carriers generated must migrate to their respective electrodes before recombination or quenching occurs. The diffusion length of an exciton is typically much less than the optical absorption length, requiring a tradeoff between using a thick, and therefore resistive, cell with multiple or highly folded interfaces, or a thin cell with a low optical absorption efficiency.
Angular-shaped 1,2,5,6-naphthalene tetracarboxylic diimide (NDI) monomers have demonstrated high conductivity in other organic electronic applications. However traditional synthetic routes created safety concerns due to the use of a toxic cyanide reagent and the use of a stainless steel autoclave for a high temperature oxidation reaction. Please see FIG. 1 for a traditional partial synthesis of NDI. There exists a need to find a synthesis method to produce NDI monomers safely.